Sunday, December 30, 2007

Those of you lucky enough to Get 4GB (or more) of RAM surely suffer from the DRN syndrome: Dumb RAM Number Syndrome. This is when Windows reports that the amount of available RAM is 3.25GB instead of 4GB, which is due to the fact that either your hardware can't support that much of memory capacity, or your OS hasn't been configured/tricked into reading high capacities.

Operating Systems Supported

Regardless of whether you have 32-bit or 64-bit hardware, if your Operating System (OS) is 32-bit, then you can't address more than 4GB, unless you enable a certain option in the OS. Before jumping into configurations, below is a list of 32-bit Operating Systems:

Linux 2.4/2.6 kernel

Windows 2000/XP/2003/Vista

Linux Specific:The wiki article (referenced below) is wrong; It states that 4GB can't be addressed unless when 2.6 kernel is used. This is not true, and here's an excerpt from my 2.4 kernel help:

If you are compiling a kernel which will never run on a machine with more than 960 megabytes of total physical RAM, answer "off" here (default choice and suitable for most users)....If the machine has between 1 and 4 Gigabytes physical RAM, then answer "4GB" here.If more than 4 Gigabytes is used then answer "64GB" here.

That can be found under "Processor type and features" -> "High Memory Support".* You need PAE support only if you have more than 4GB, if you have 4GB or less, you don't need PAE.On a 2.6 kernel, the support for 4GB RAM or more is automatically enabled, as far as I know.

Windows Specific:PAE support is not enabled by default on compatible hardware, so you have to do it yourself.First check whether your hardware is supported or not, then follow the steps to enable PAE.

Hardware Support

To be able to configure the OS to see 4GB or more, you need hardware support from the processor.

Windows users skip this step and go to the section where PAE is setup. If that doesn't work, come back and read this section.

Instead of boggling your head and going on a Googling frenzy try to figure out whether your processor has that ability or not, the easiest way is to download a Linux LiveCD (192MB), which will basically run Linux OS from the CD, without touching your hard disk. After you download the ISO file, use a CD burning utility to burn the ISO file CD image to a CD (don't copy the ISO file to the CD!). Then put the fresh CD into the CD-bay and reboot your computer (make sure the CD boot order is before the hard disk -- check your BIOS setup options). Once the CD boots, you'll get a black screen with some text here 'n there, type the user as root, and the password as toor. Then execute the command:

As you can see, pae is among the clutter, which means that your processor supports having 4GB or more.

* If the LiveCD doesn't boot, it's most likely that you have crappy old hardware, so don't bother reading the rest of this post!

PAE

I guess you're sick of seeing this PAE word over & over & over & over & ... Well, PAE means Physical Address Extension (PAE).Hoping that you still a few working brain-cells, after banging your forehead for not figuring that out sooner, below are the steps to enable PAE on Linux & Windows.

Linux:- For 2.4 kernels, you need to recompile your kernel. (If you don't know to do so, visit LinuxQuestions.org and read the forums).Make sure to specify the proper option in "Processor type and features" -> "High Memory Support": 4GB for machines with 1-4GB of RAM, and 64GB for machines with more than 4GB of RAM.

- For 2.6 kernels, as far as I know, 2.6.18+ should have that option enabled by default to handle 1-4GB or more. If you can prove otherwise, please let me know.

Windows:- XP/2003: Right click "My Computer" -> "Properties" -> "Advanced" -> Startup section "Settings" -> "Edit" -> Add "/PAE" without the quotes at the end of the last line (not the blank line!) -> Save the file and close it -> OK all the way & reboot.

- Vista: I have no clue, as I have no access to a vista machine, but a decent Google query should do it. (Something like: windows vista PAE how)

If you had done the configurations above and Windows stopped booting for you, this probably means that you don't have PAE support. You can undo your evil trick, by booting into "Safe Mode" and removing "/PAE" and rebooting again.To be sure whether your processor supports PAE or not, read the hardware section at the top. All of it!

Testimonials

You don't see this often, but I'm going to take my own testimony! I tried the above with a Windows machine running on a 64-bit XEON (EM64T) processor with Windows 2003 Standard installed. After enabling the PAE switch, the server was able to see all 6GB of RAM installed, where it saw 3.25GB only before.

I'll be buying 8GB of RAM soon for my home machine, and I'll update this post on the results.

Friday, December 28, 2007

I was able to successfully install VMware Server on my Slamd64 box. I had a few problems here & there, and had a tough time gathering the pieces, so I thought I'd mention them. (I have posted on Slamd64's forum as well)

Some steps are similar to those when installing VMware workstation on Slackware, and have been copied from online pages. The links to these resources are found at the end.

First, make sure that you have the following package (or newer): gcc32-4.1.2-x86_64_slamd64-2.tgzThis is mandatory to run vmware console properly on any 64-bit Linux distro. Without that package, the VMware console will be able to connect, but will not allow you to create any VM.

You will also need the kernel source package; if you're using the stock kernel (the default), the source for it is on the installation CD, under the name "kernel-source-2.6.18.8_smp-noarch_slamd64-1" and can install it using "pkgtool", otherwise if you had compiled your own kernel, you should be OK.

Now, that you have downloaded the VMware packages & installed gcc32, proceed with these steps:

1st we need to create the init directories in a way VMware likes

cd /etcmkdir init.dfor i in {0,1,2,3,4,5,6}; do mkdir rc$i.d; done

# Side Note# Since VMware will run suid root, you might want to limit program execution# to a particular group of users (I created a 'vmware' group in /etc/group and added the desired users). Refer to the reference link at the end for more info.

First, unpack the server

tar -xf VMware-server-1.0.4-56528.tar.gz

cd & start the installation -- go with the defaultsWARNING: The last step will ask you to run vmware-config.pl , choose NO!

You should be able to access the web interface at https://localhost:8333 ; Use your system username & password to login. The web interface doesn't allow you to create VMs. And it doesn't work properly with Konqueror.If you want the graphical console, run vmware.

You might want to chown the directory where you save your VMs, /var/lib/vmware/vms in my case, to your user, so you could have write access.

After some unfortunate accidents in the past, where data was *almost* lost, I decided to take certain precautions to make sure my data is safe.I've been a Slackware Linuxuser abuser for around 5 years now, and have recently moved to Slamd64, which is a port of Slackware for 64-bit hardware (64-bit OS). I used Linux's software RAID capability to build a RAID5 array of 3x 320GB disks, yielding in 590GB of storage space. (the wasted space is for swap partitions, boot partitions and filesystem size).As of this writing, I have 96.1GB left, and I still haven't copied my old data!

Why not an OTS?

To understand why I'm building one from scratch, rather than getting one of those off-the-shelf (OTS) Network Attached Storage (NAS) devices, one would have to understand the problems of the OTS devices:

OTS NAS devices come with a built-in hardware RAID controller; If that controller got busted/burnt, you can no longer access your data, unless you buy ANOTHER device of the same brand (all hardware RAID controllers use proprietary methods to store data).

If one of the disks fail, you have to buy a replacement disk of the same brand AND model number (limitation of the hardware controller), which is most likely not possible, unless you buy another NAS device of the same brand, hoping to have the same old disks.

To extend your current storage, you have to buy another NAS, as there's no way to expand/stack an existing one.

What does a home-brew NAS offer?

It depends on your approach, and design of the NAS, and of course, budget!I'm planning an initial 4TB NAS, to withhold ALL my data, and data of other family computers in the house (either directly, or backed to the NAS). So, my budget is kind of flexible, but I'm all for cheap stuff, so I'll squeeze the money out of every item I buy!

Getting to the point, the NAS I have in mind, will offer the following:

Early detection of failures: By using software that monitors the disks, whenever something fails, or errors start occurring, send an email.

One could argue that current OTS NAS devices that offer 2TB are cheaper than building one from scratch, which might be true, but most likely would not offer any of the advantages above, and would suffer from all disadvantages. And, on the long run, using a home-brew one, would prove to be cheap, when expanding to extra storage, as demand grows.

Points of caution with a home-brew

If you aren't careful with your design and implementation, you could seriously jeopardize your data.

Before jumping into scenarios, I should mention this info, in case you didn't know it: Linux's RAID arrays can be built on partitions & block devices, that is, you can create a RAID5 array of 5 partitions on the same disk, or of different disks!

Now, consider the following:

Scenario 0 - Expansion: Let's say I have a RAID5 array of 5x 500GB disks, and have consumed 90% of it. Time to expand! Unfortunately, the market no longer has 500Gb disks, so let's say we have 750GB disks. When adding the new 750GB disk, I'd have to partition it into 1x 500GB & 1x 250GB, because the smallest disk size in the array is 500GB. The remaining 250GB partition can be treated as a standalone partition and not part of an array. (its contents can be backed up to the array, though).

Scenario 1 - Expansion: Instead of buying a new 750GB disk, I bought a 1TB disk. The WORST idea ever is to partition the disk into 2x 500GB partitions and adding BOTH to the RAID5 array; why is that so bad? because if the 1TB disk failed, I'd lose 2 pieces of the array, not just one, and hence, loose ALL my data residing on that array!!A workaround, is to join one partition into the array, and put the other as a standalone.

Scenario 2 - Replacement: Let's say I have a RAID5 array of 5x 500Gb disks. One disk made a bobo and died on me. The above solutions of the Expansion scenarios apply here, as well.

Design

All disks will fit in a rack/case, with a built-in Power Supply Unit (PSU)

Next to the disk rack, is a motherboard rack/stack; they'll act as management computers. Each motherboard should have 6-8 SATA2 ports handled by the chipset directly, not by a controller*.

SATA data cables are extended from the disk rack to the management stack.

All racks are powered through a UPS. The management boxes monitor the UPS's battery status, and put the disks in sleep mode then shutdown automatically when needed. (Or shutdown the disk rack if possible to shutdown the specific UPS port)

Management boards will boot the OS from a USB memory stick, because it's cheaper than a hard disk (and faster)

Next to the disk rack, is a motherboard rack/stack, which will have multi mini/nano ITX boards; they'll act as management computers

Management boxes must have built-in SATA 2 ports and one PCI slot. A PCI-to-SATA adapter will be connected to provide more SATA ports. The max is around 6 ports per board, that is 6 managed disks. This assures that if one management box dies, some data is still accessible.

* Because the controller communicates via the PCI bus, which has a lower speed than that of the chipset, and all ports connected to the controller will be sharing a single bus. Ports that are handled by the chipset are independent.* 32-bit PCI buses have a max throughput of 133 MB/s, while the common PCIe 1.1 has a max of 250 MB/s, and PCIe 2.0 has a max of 500 MB/s.This means, having a PCIe 1.1 adapter/card with 4 SATA2 ports, will result in limiting the max throughput of the disks to 250 MB/s, instead of 300 MB/s per disk, because all the disks connected to these 4 ports are sharing a single bus.One could have multiple PCIe cards, but create RAID arrays of one disk from each card; This would work for non-high-load configurations. Under high load.

Figure 0 is the old design, which I scrapped (using mini/nano itx motherboards & PCI).Figure 1 is the new approach and shows 2 ways to implement a NAS:

The first is more suitable for environments where there's no dust accumulation, like server rooms, or if you like the occaisional dust-blowing adventures... It also depends on the space available for future growth.Note that those disk-specific racks come with their own power supply, which is different than a typical power supply, because it has power pins for disks only, no motherboard pin.

A good reason to go for the 2nd is if the case supports multiple power supplies, for redundancy. Useful for critical machines.Pay extra attention to the power supply & make sure it can support the max number of disks your motherboard allows.

Market evaluation

The prices of computer hardware in Kuwait are very high, and depending on the total cost of the project, one must see whether it's worth buying from the Internet, or not.As of this writing, the price of a 1TB disk = 100 K.D., and 500GB = 40 K.D., in Kuwait, while online, 500GB = 25K.D. and 1TB = 74 K.D. ($1 USD = 0.2743 K.D.). So, if you decide to buy 3x 500GB disks, you'd save 45 K.D., take 30 K.D. out for shipping (assuming worst case), you still save 15 K.D.!Note, that on 1Tb disks, you save 25 K.D. per disk, so for 5 disks, that's 125 K.D., minus 45 for shipping (assumption), you save 80 K.D.!!!! These savings can get you a management computer!So, as far as I'm concerned, I'll be buying from the Internet, to avoid the absurdly high expenses of the local market.